Since the late 1980s, a variety of retractable needle injection syringes have been developed to decrease the risk of needle stick injuries after intravenous or intramuscular administration of fluid medication. Such syringes may be broadly categorized as having a manually retractable needle or an automatically retractable needle. In manually retractable needle syringes, the piston of the syringe is adapted to engage the needle or the needle hub and to permit the needle or hub to be withdrawn into the barrel of the syringe when the piston is pulled rearwardly after an injection stroke. Such syringes are exemplified by U.S. Pat. No. 4,507,117 to Vining et al.; U.S. Pat. No. 4,692,156 to Haller; and U.S. Pat. No. 4,710,170 and numerous later variations thereof, to Haber et al.
In automatically retractable needle syringes, a spring-loaded retraction mechanism is provided for driving the needle into an interior compartment upon actuation of a latch associated with the retraction mechanism. Such syringes are shown and described in U.S. Pat. No. 4,994,034 to Botich and Halseth.
Prior to retracting the needle, the aforementioned retractable needle syringes are used in substantially the traditional manner, e.g., by initially drawing fluid medication into the syringe by inserting the needle into a supply of medication, and then withdrawing the piston in order to draw the medication into the barrel of the syringe. Then, the dosage of the medication is adjusted, and air bubbles removed from the barrel, by ejecting a portion of the withdrawn medication from the syringe while holding the syringe in an upright position. The traditional practice for preparing an injection can be wasteful, hazardous, and can lead to dosage errors. Moreover, in an emergency situation, precious moments can be lost while an injection is prepared. To circumvent these problems, several types of pre-filled injection systems, such as Sterling Winthrop's “CARPUJECT”, Wyeth-Ayerst Laboratories' “TUBEX” and Abbot Laboratories' “ABBOJECT” injection systems, have become popular alternatives to the traditional vial-and-syringe method of storing and administering injectable medications.
It would be desirable to provide the advantages of automatic needle retraction for pre-filled fluid medication injection systems and to further improve such pre-filled injection systems for reduced manufacturing costs and enhanced ease of use. Because of the substantial market penetration and professional acceptance of the aforementioned commercially-available injection systems, it would also be desirable to provide automatic retraction capability for pre-filled injection ampoules.